Electromagnetic horn



Jan. 5, 1943. w. L. BARROW ELECTROMAGNETIC HORN Filed Aug. 27, 1958 4 Sheets-Sheet 1 INVENTOR MAME/P BAR/WW WEN WQ qxbms bx Mx ATTORN EY Jan. 5, 1943. w, BARROW 2,307,911

ELECTROMAGNETIC HORN Filed Aug. 27, 1938 4 Sheets-Sheet 2 MW m ATTORNEY ELECTROMAGNETIC HORN Filed Aug. 27, 1938 4 Sheets-Shet 3 ill" I INVENTOR MAME/P LEAR MW ATTORNEY Jan. 5, 1943. w. BARROW ELECTROMAGNETIC HORN Filed Aug. 27, 1938 4 She ets-Sheet 4 INVENTOR W/LMER L. BARR W M 14 ATTORNEY t -l Jan. 5,

C'I'BOMAGNETIC HORN ei- Barrow, Newton; Mesa, assignor to ch Corporation, New York, N. Y a corporation oi New York Application August 27, 1938, Serial No. 227,183

(El. 25ll-ll1) 52 Claims.

The present invention relates to electromagnetic horns.

It has heretofore been proposed to excite a horn by means of a hollow-pipe wave-guide transmission line or chamber connected to the throat of. the horn, with an antenna or other translating apparatus positioned in the pipe, at the rear of the horn. For transmission purposes, the proposal has been to employ the antenna as a medium for exciting waves in the hollow pipe.

These waves may be transmitted through the pipe to the throat of the horn, then through the horn to its mouth, and finally, beyond the mouth of the horn, into free spac as ordinary radio waves. A similar but reverse process may take place in reception.

An object of the present invention, however, is to position the antenna or other translating apparatus directly in the throat of the horn, without the use of a hollow-pipe, waveguide transmission line. The translating apparatus should be positioned in the horn outwardly of any portion thereof that may be of substantially uniform cross section, and not in a wave guide or chamber that may be attached to the horn. When used as a transmitter, the horn will then operate to excite directly waves of horn type, or "horn waves, and a beam will be radiated from the horn mouth of character appropriate to the horn itself, rather than to the antenna and other apparatus. Thehom, furthermore, will operate eficiently to receive from space substantially all of the incident energy, when used as a receiver. With the antenna or other apparatus in the throat, furthermore, the horn has smaller physical dimensions than when connected to the hollow 'pipe.

Other and further objects will be described hereinafter and will be particularly pointed out in the appended claims.

The invention will now be described in connection with the accompanying drawings, in which Fig. 1 is a diagrammatic view of circuits and apparatus adapted for transmission according to the present invention, showing. in longitudinal section, an electromagnetic horn -connected to a suitable sending equipment; Fig. 2 is a similar view of a modified arrangement; Fig. 3 is a longitudinal cross section through a modifled horn, with vacuum-tube apparatus disposed directly in the throat ofthe horn and embodying also an adjustable plunger; Fig. 4 is a perspective of the plunger shown in Fig. 3; Figs. 5 and 6 are diagrammatic views illustrating circuits and apparatus for use with the modification of Fig. 3 for transmitting and receiving, respectively, in accordance with the present invention and illustrating also modified plungers; Fig. 7 is a front view of the apparatus shown in Fig. 6; Fig.8 is a view similar to Fig. 3 of a further form that the apparatus of Fig. 3 might assume; and

- Fig. 9 is an equivalent circuit diagram.

In Fig. 1,- there is shown a system comprising a radio-frequency oscillator 2, connected with a modulator 3. which may be modulated in any desired way, as bymeans of a microphone 4. The modulated output may be fed to a radiofrequency amplifier 6 that may be coupled to a circuit 8 having balanced parallel-line or biconductor output leads I0 and I2. Sending or receiving apparatus may be connected to the two-wire connecting leads I0 and I2.' The leads I0 and I2 are shown, in Fig; 1, connected to a projecting metal exciting or absorbing antenna rod or rods IE, or other energy-translating apparatus, disposed approximately centrally, directly in the throat or small or reflecting end of an electromagnetic horn I6. outwardly of am; portion thereof at the small end of the horn,

- such as an elongated tubular or pipe body portion or section I8, that may be substantially uniform in cross section. A similar construction is shown in other figures. Vacuum-tube or other energy-translating apparatus I20 may be mounted, together with the antenna rod or rods I30, in the throat of the electromagnetic horn I22, outwardly of any portionvthereof at the small end of the horn, such as the elongated tubular or pipe body portion or section 57, that may be substantially uniform in cross section.

The antenna rod I3 is similarly shown positioned in the throat of the horn in Fig. 2. The conductor I3 is shown supported in and spaced from the walls of the tube I8 by insulating members I9. The wires I0 and I2 of Fig. 1 and similar members in other figures may be similarly supported, but the supports are omitted, for clearness.

The exciting or absorbing rod or rods I3, I4 and I30 for exciting or intercepting the electromagnetic waves may be connected to terminal apparatus at the smaller end of the horn. This terminal apparatus may be connected either to sending or to receiving apparatus at a sending or receiving station. Any of the horns illustrated and described herein may be used either for transmission or reception of-ultra-high frequency electromagnetic waves.- The energy will thusbe either radiated from-the horn 46 or I22 or it will be received by the horn and demodulated. As

the translating apparatus is positioned directly in the throat of the horn, in order directly to excite the horn, in transmission the modulated ultra-high frequency energy may be taken by the conductors from the sending apparatus at the small end of the horn and delivered to the horn, to be propagated through the interior of the horn to the mouth as "horn waves." At the large end or mouth of the horn substantially all of this modulated ultra-high frequency energy will be radiated out into free space by the horn as ordinary radio waves. When used for transmission, the horn It or I22 thus may constitute a directive electromagnetic radiator. Similar,but reverse, operation will take place for reception, the large end or mouth of the horn being electromagnetically open to space to permit the horn to receive electromagnetic waves from space. In receiving, the electromagnetic waves received at the mouth of the horn will be conducted down the horn to be delivered to the receiving apparatus, and the signal comprising the intelligence will be recovered by demodulation. No wave guide or chamber, resonant or otherwise, need be provided for generating the waves or receivinz them.

The horn may be constituted of a formed sheet of conducting material, like} metal, such as copper or aluminum, or it may be constituted of other material if its inner wall is otherwise rendered a conductor of the said waves. The space inside the horn, being open to the atmosphere. is naturally a non-conductor. The principal axis of the horn extends between the smaller and the larger ends of the horn.

Though the invention is illustrated by Fig. l in connection with a conventional parallel-line system, it may be employed also with coaxial-line systems, or to any other desired connecting system. One of the wires, as the wire I of Fig. 2, may be connected to the outer tubular conductor I8 of the coaxial feed line or the pipe 51 of Fig. 3. The other wire, as the wire I2, may be extended into the bell of the horn, axially thereof and of the tubular body portion I8, to form the center or inner conductor of the coaxial line, as illustrated at I3 in Fig. 2. In this modification, the element I3 constitutes the absorbing or exciting antenna for exciting or absorbing longitudinally polarized waves.

The translating apparatus I may be supported upon a dielectric or insulating support I22, shown in Fig. '7 as fixed to opposite sides of the horn, centrally of its throat.

The horns I6 and I22 are each illustrated as constituting a flared-out continuation, at the free open end, of the elongated tubular or pipe portion or section I8 or 51. The portion I8 or 51 may extend over any desired distance from the throat of the horn, to the left, as viewed in Figs. 1, 2, 3, 5, 6 and 8.

The leads I26 may extend through an opening in a conducting barrier I23, disposed in the body portion 51, near the small end of the horn, for supplying power and signal-modulating voltages to the tube I211. The barrier I28 may, if desired, corresponding to the barrier 59, be constituted of an adjustable closing reflecting metal or other conducting piston or plunger near the throat or back of the horn, in which event the leads I26 may be carried out through some other part of the horn. The leads I33 and I35 of Figs. 6 and '7 extend through openings in the wall of the horn to connect a vacuum tube I56 and radio-frequency choke coils Ill to apparatus outside of the horn.

The leads I26 and the leads I33, I33 may be spaced from the walls of the tube 51 by insulating members (not shown). The pipe portion I3 or bl may constitute a shield for the two-wire line Ill, I2, in Fig. 1, or the wires or leads I26 and other apparatus contained therein, in Fig. 3, or the leads I33, I35.

The rods It and I30 are shown disposed substantially at right angles to the principal axis of the horns I6 and I22, respectively, but, in certain other modifications, they may be disposed unsymmetrically in the horn, to give a modified directive pattern for the radiant energy. With the antenna rods I l and I30 constructed and positioned as illustrated, electromagnetic waves produced thereby in the small end of the horn will be transversely polarized; that is, the electric intensity will be entirely in surfaces normal to the direction of propagation.

The electromagnetic horn need not be circular .or round in cross section, as in Figs. 1 and 2; it

may, for example, be of simple rectangular shape, as shown at I22 in Fig. 3, the corresponding body pipe portion 51 of which, from which it flares out, being likewise rectangular. For beam transmission, a horn of rectangular cross section, with an orientation of the exciting rod perpendicular to the horn axis, offers certain features, among them the important feature of a radiated space wave polarized with the electric vector mainly in a single direction. The rectangular cross-section may be such that the sides of the horn shall flare in four oppositely disposed directions, or two of the sides may be substantially parallel. Other shapes also may be employed, either for receiving or sending.

Fiat-sheet reflectors and reflectors that are concave, like parabolic and semi-spherical, have been used heretofore to yield directive radiation with exciting rods and antennas; but as reflectors only. The differences between a reflector and the electromagnetic horn of the present invention may be understood from the following considerations. The function of the electromagnetic horn is to guide waves traveling within it and tangentially along its surface in the longitudinal direction, smoothly and without interruption. The direction in which it is desired to launch the waves into space is determined by designing the horn so that it shall have a guiding surface or guiding walls in the desired direction connecting the small and the large ends of the horn. The guiding walls guide the waves received from space at the mouth of the horn to the throat end of the horn, or they direct, for radiation, forward out into space the waves generated at the small end of the horn. A wave reflector, on the other hand, does not guide waves traveling along its surface; there are no waves, indeed, traveling along this surface. The reflector does not and can not mold, form, guide and transmit waves of the character employed in the electromagnetic horn. A wave reflector receives waves traveling at an angle of incidence toward the reflecting surface, abruptly stops them, and then sends them away from the surface out into space at a different angle to the surface, which different angle is known as the angle of reflection. In accordance with geometric-optic principles, the angle of incidence is equal to the angle of reflection.

In the electromagnetic horn, furthermore, the waves travel with a phase velocity substantially a particular kind of terminal device.

diflerent from that of light in the medium of the horn. Near the small end of the horn, the phase velocity may be very much greater than the velocity of light. The phase velocity decreases as the large end or mouth of the horn is reached until, just at or beyond the mouth of the horn, the phase velocity may be exactly the same as that of light.

In the electromagnetic horn, the waves may be regarded as traveling in the dielectric of the space in the horn, continuously outward along the inside conducting horn surface, toward free outer space. The flared horn provides a surface of progressively greater cross-sectional area as the wave travels outward, causing the wave energy to spread over a relatively large area at the mouth for directive transmission, but in such a manner that the wave energy is continuously and smoothly guided and the field configuration of the wave is reasonably maintained during its outward progression. The waves become thus slidingly attached to the inside horn surface, and they remain so continuously attached throughout their sliding movement along this inside horn surface, from the small or throat end of the horn until they reach the mouth of the horn. It is in this manner that they become guided by the surface during such travel outward. Upon arrival at the mouth of the born, the waves become readily disattached from the horn surface, but they continue thereafter to travel into free space, forward in the desired direction of progression of the waves predetermined by the design of the horn. No such action takes place with wave reflectors.

It is, therefore, possible to design horns of a large variety of shapes. The focus-forming surfaces usually found at the small ends of parabolic reflectors, furthermore, are not needed according to the present invention. It is desirable to initiate the waves at the small'end ofthe horn in some other manner, such as described herein.

That the horn of the present invention. does not depend on reflection is further evident from the different nature of transmission and reception of the waves.

Electromagnetic horns bear a slight analogy to acoustic horns. Though the cross-sectional dimensions of the throat of an acoustic horn are usually much smaller than the length of the acoustic wave, in electromagnetic horns, the cross-sectional dimensions of the throat are comparable to the length of the electromagnetic wave.

The electromagnetic horn, like the hollow pipe, may be operated with one, or'with several, of many possible distinct wave types, each of which may be separately excited by, or is responsive to, The space wave radiated by the horn in beams of different configurations, and the response of a receiving horn to waves arriving at different space angles, depends, in part, on the shape of the horn in all cross sections. Terminal devices for longitudinal waves are fundamentally different in construction from those for transverse waves. Different types of horn waves, and combinations of the same, may be separately excited and propagated within the horn, or absorbed by the horn, by properly arranging the exciting rods or rods in the throat of the horn. Both the position of, and the current in, the rod or rods may be varied. The type of wave, and hence the configuration, of the lines of electric and magnetic force, into which the electromagnetic wave that is transmitted down the horn may be revolved, depends on the frequency and on the design of the terminal device. The choice of the type of the wave that is to be transmitted influences, therefore, the design of the terminal. In general, there are two distinct groups of waves: E-waves, having a radial componentthat is, a component in the direction of propagation of the waves within the hornof electric intensity, but no radical component of magnetic intensity, in the hem; and H-waves, having a ra dial component of magnetic intensity, but no radial component of electric intensity, in the horn. Two subscripts are needed to define the waves of difierent orders. The subscripts n and m are used, each representing a positive integer, denoting the number of half-sinusoid variations in the field between the top and the bottom and the two side walls, respectively. Thus, we have the Hn,m and the En,m types of waves. The arrangement of antenna shown in Fig. 7, for example, is appropriate to the lowest-order H wave, designated Hm. Other terminals are appropriate to E-waves, and so on.

These waves will not be more fully described herein because they will be understood without further description by reference to a paper by L. J. Chu and W. L. Barrow, entitled,"Electromagnetic waves in hollow metal tubes of rectangular cross section," Proceedings of the Institute of Radio Engineers, vol. 26, No. 12, December, 1938, commencing at page 1520, and also to a paper by Barrow, entitled, Electromagnetic-ham radiators, Union Radio Scientifique Interna tionale, No. 79, p. 277, containing a revision of a paper presented at the Joint Meeting of the said Union and the Institute of Radio Engineers, at Washington, D. C., April 30, 1938. See also a paper by W. L. Barrow and L. J. Chu, entitled, Theory of the. electromagnetic horn, Proceedings of the Institute of Radio Engineers, vol. 27, No. 1, January, 1939, commencing at page 51, and also a paper by W. L. Barrow and F. D. Lewis, entitled, The sectoral electromagnetic horn, Proceedings of the Institute of Radio Engineers, gel. 27, No. 1, January, 1939, commencing at page The vacuum-tube apparatus I20 or I56 may be of any desired type, depending upon the use to Cal which it may be put; it is shown as a high-vacuum diode rectifier or detector, but it may, for example, be a Barkhausen tube, a triode, or a magnetron. Any of these, and also a crystal detector, may be connected in series with the rod or rods, such as the rods IE or I30, with or without a by-pass condenser, as hereinafter explained. It may also be of the Peterson type described in the General Radio Experimenter for October, 1937.

The conducting piston plunger 59 or I28 may be adjusted, as by means of a handle I29, for varying the distance between the antenna rod or rods I30 and the conducting closure I28. This adjustment makes it possible to resonate or tune the throat of the horn, thereby rendering the throat of the horn more responsive to a particular frequency or a narrow band of frequencies than to other frequencies. Optimum conditions for operation may be provided also in other ways.

Oneform, that the transmitting connections may take is illustrated in Fig. 5, in connection with a tube I20 of the Barkhausen type. Leads I32 and I34 connect a heating battery I35 to the filament I38 of the tube. The conductor I32 and a conductor I40 connect the filament I38 and the plate I42 to a plate battery I. A battery I46 applies a positive bias, through a conductor I48,

to the grid I60 oi the tube. The radio-frequency oscillator may be modulated in any desired way, as by means of modulating currents introduced through the medium of a modulating transformer I62, the secondary winding I60 of which is shown connected in the filament-plate circuit, in the conductor I40,

The receiving connections may take the form illustrated in Fig. 6. The vacuum tube is here, as in Fig. 3, shown as .a high-vacuum diode rectifier or detector I56. The modulated electromagnetic energy received by the antenna I30 of the horn I22 will, after demodulation, be amplified by an amplifier 36, and the amplified energy will be detected by a detector 31 coupled to the amplifier and evidenced in a loud-speaker or telephones 38 connected to the detector 31. The direct or other demodulated current may be led out of the horn through radio-frequency choke coils I3I to the amplifier and the ear phones. The choke coils I3I prevent the passage of radio-frequency energy outside of the horn, except at the mouth of the horn.

The choke coils I3I of Fig. 6 may, however, be

replaced by a by-pass condenser in the horn,

as shown at I61 in Fig. 8. The high-frequency currents will, in both cases, be confined entirely inside the horn.

The lead I36 extends to the filamentary cathode and the leads I33 to the anode or plate of the diode I56. Power supply and modulating current leads are carried into the detector I66, preferably through a shield, and preferably at right angles to the antenna. The distance between the plunger 59 and antenna rod or rods I30 should be adjusted for maximum effect; if the plunger 59 is replaced by a fixed wall, the detector I56 and the antenna rod or rods I30 may be made adjustable by sliding back and forth along the axis of the horn to accomplish the same result. This may be desirable, for example, if the small end of the horn is continued to form an apex (not shown), as illustrated and described in a copending application, Serial No. 230,737, filed September 19, 1938.

The energy-translating means and the antenna are shown in Fig. 3 as both in the throat of the horn. In the form of Figs. 1 and 2, however, the exciting or absorbing rod is in the throat. but

the electric circuits and apparatus and other ena ergy-translating means are outside the horn.

As illustrated in Fig. 8, the antenna rods I30 may take the form of alined shielding tubes I68 and I60, the former integral with, and extending inward from, the horn, and the latter integral with one side of the condenser I51, the other side being constituted of an adjacent wall of the horn. The leads I62 from the triode detector or oscillator I60, which may also be shielded, disposed in the born between the tubes I60 and I62, may

extend out of the horn through the interior of the tube I60, to an audio-output circuit I66, couled through a transformer I68. The oscillator I 60, with its auxiliary apparatus, may be mounted on a metal shield (not shown) at the free end of the tube I60. One of the leads I10 may be connected, through an impedance I10 and a condenser I12 in parallel thereto, to the tube I60. The equivalent circuit diagram is shown in Fig. 9, like parts being indicated by like reference numerals. The equivalent of the condenser I61 is not illustrated in Fig.9.

The invention 15 not limited to the exact embodiments thereof that are illustrated and described herein; further modifications may be made by persons skilled in the art without departing from the spirit and scope .of the invention, as defined in the appended claims.

What is claimed is:

1. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, absorbing or exciting antenna means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the antenna means at the small end with a phase velocity substantially diflerent from that of light in the medium of the horn in order that the received waves may be absorbed by the antenna means or for guiding to the large end with a phase velocity substantially difierent from that of light in the medium of the horn for radiation out into space the waves excited by the antenna means at the small end, and means for connecting the antenna means with means for evidencing the received waves absorbed by the antenna means or with means for energizing the antenna means to excite at the small end the waves to be radiated out into space.

2. A receiving system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space, an absorbing antenna disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the antenna at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the antenna, and means for connecting the antenna with means for evidencing the received waves absorbed by the antenna.

3. A sending system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to radiate electromagnetic waves out into space at the large end, an exciting antenna disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the antenna at the small end, and means for connecting the antenna with means for energizing the antenna to excite at the small end the waves to be radiated out into space.

4. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, absorbing or exciting antenna means disposed in the horn at the small end outwardly of any portion thereof that may be at substantially uniform cross section, the

horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the antenna means at the small and with a phase velocity substantially diflerent from that of light in the medium of the horn in order that the received waves may be absorbed by the antenna means or for guiding to the large end with a phase velocity substantially difierent from that of light in the medium of the horn for radiation out into space the waves excited by the antenna means at the small end, and bi-conductor means for connecting the antenna means with means for evidencing the received waves absorbed by the antenna means or with means for energizing the antenna means to excite at the small end the waves to be radiated out into space.

5. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, absorbing or exciting antenna means disposed in the horn at the small and outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the antenna means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the antenna means or for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the antenna means at the small end, and shielded parallel-line means for connecting the antenna means with means for evidencing the received waves absorbed by the antenna means or with means for energizing the antenna means to excite at the small end the waves to be radiated out into space.

6. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, absorbing or exciting antenna means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the antenna means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the antenna means or for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the antenna means at the small end, and coaxial-line means for connecting the antenna means with means for evidencing the received waves absorbed by the antenna means or with means for energizing the antenna means to excite at the small end the waves to be radiated out into space.

7. An electric system having, in combination,

an electromagnetic-wave-guicle horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, and an absorbing or exciting antenna rod disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section substantially at right angles to the axis of the horn for absorbing or exciting transversely polarized waves, the horn having guiding walls between the large end and the small and for guiding the waves received from space at the large end to the antenna rod at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the antenna means or for guiding to the large end with a phase velocity substantially difl'erent from that of light in the medium of the horn for radiation out'into space the waves excited by the antenna rod at the small end.

8. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, and an absorbing or exciting antenna rod disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section substantially along the axis of the horn for absorbing or exciting longitudinally polarized waves, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the antenna rod at the small end with a phase velocity substantially diiferent from that of light in the medium of the horn in order that the received waves may be absorbed by the antenna means or for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the antenna rod at the small end.

9. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, absorbing or exciting antenna loop means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at'the large end to the antenna means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the antenna means or for guiding to the large end with a phase ve-' locity substantially different from'that of .light in the medium of the horn for radiation out into space the waves excited by the antenna means at the small end, and shielded parallel-line means for connecting the terminals of the antenna loop means with means for evidencing the received waves absorbed by the antenna means or with means for energizing the antenna means to excite at the small end the waves to be radiated out into space.

10. An electric system having, in combination, an electromagnetic-wave@guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, and absorbing or exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially diiferent from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end.

11. A receiving system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the hornto receive electromagnetic waves from space, and absorbing translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end with a phase velocity substantially different from that of light in themedium of the horn to the translating means at the small end in order that the received waves may be absorbed by the translating means.

12. A sending system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to radiate electromagnetic waves out into space at the large end, and exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end.

13. An electric system having, in combination,

an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive modulated electromagnetic waves from space or to radiate modulated electromagnetic waves out into space at the large end, absorbing or exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end, and means for connectng the translating means with means for demodulating the received waves absorbed by the translating means or with means for energizing the translating means to excite at small end the modulated waves to be radiated out into space.

14. A sending system having, in combination, an electromagnetic-wave-gulde horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to radiate electromagnetic waves out into space at the large end, exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding to the large end for radiation out into space the waves excited by the translating means at the small end, means for energizing the translating means to excite at the small end waves to be radiated out into space of a character such that they shall be propagated through the horn from the small end to the large end with a phase velocity exceeding that of light in the medium of the horn, and means for connecting the translating means with the energizing means.

15. A sending system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to radiate electromagnetic waves out into space at the large end, exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding to the large end for radiation out into space the waves excited by the translating means at the small end, means for energizing the translating means to excite at the small and waves to be radiated out into space of a character such that they shall be propagated through the horn from the small end to the large end with a phase velocity that is substantially greater than that of light in the medium of the horn near the small end and of diminished velocity in the medium of the horn near the large end, and means for connecting the translating means with the energizing means.

16. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, an insulating support fixed in the horn at the small end, and absorbing or exciting translating means supported by the support in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the receiving waves may be absorbed by the translating means or for guiding to the large end With a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end.

17. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, an insulating support fixed in the horn at the small end,and absorbing or exciting translating means supported by the support in the horn at the small end outwardly oi any portion thereof that may be oi! substantially uniform cross section, the translating means comprising vacuum-tube apparatus and an antenna connected thereto and positioned substantially at right angles to the axis of the horn, and the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially difierent from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end.

18. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, and absorbing or exciting translating means adjustably disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from spaceat the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially diiferent from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end.

19. An electric system having, in combination,

an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, the horn being provided with a barrier at its small end, and absorbing or exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially difierent from that of light in the medium of the small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, two elements one of which comprises a barrier and the other of which comprises absorbing or exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier, the relative positions of the two elements being adjustable, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially difierent from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end.

21. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, a pipe joined to the small end, a conducting barrier adjustably disposed in the pipe near the junction of the pipe to the small end, and absorbing or exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially difierent from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end;

22. An electric system having, in combination,

an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into .space at the large end, the horn being provided with a barrier at its small end, the barrier being provided with an opening, absorbing or exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially difierent from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end, and means extending through the barrier opening for connecting the translating means with means for evidencing the received waves absorbed by the translating means or with means for energizing the translating means to excite at the small end the waves to be radiated out into space.

23. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, and absorbing or exciting translating means disposed in the horn at the small end, the translating means comprising vacuum-tube apparatus and, connected thereto, an antenna and means for preventing the passage of radio-frequency energy outside of the horn except at the large end of the horn, the preventing means comprising a condenser, and the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end in order that the received waves may be absorbed by the translating means or for guiding to the large end for radiation out into space the waves excited by th translating means at the small end.

24. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, an insulating support fixed in the horn at the small end, and absorbing or exciting translating means supported by the support in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the translating means comprising vacuum-tube apparatus and an antenna connected thereto, the antenna comprising substantially alined tubes, and the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end.

25. An electric system having, in combination, an electromagnetic-Wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, an insulating support fixed in the horn at the small end, and absorbing or exciting translating means supported by the support in the horn at the small end, the translating means comprising vacuum-tube apparatus and an antenna connected thereto, the antenna comprising substantially alined tubes, one of the tubes being fixed to the horn, a two-terminal condenser in the horn at the small end, one terminal of the condenser being constituted of a wall of the horn, the other terminal of the condenser being fixed to the other tube, and the horn having guiding walls between the large end and the small end for guiding the waves received means at the small end in order that the received waves may be absorbed by the translating means or for guiding to the large end for radiation out into space the waves excited by the translating means at the small end.

26. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, an insulating support fixed in the horn at the small end, and absorbing or exciting translating means supported by the support in the horn at the small end, the translating means comprising vacuum-tube apparatus and an antenna connected thereto, the antenna comprising substantially alined tubes, the horn having guiding walls between the large end and. the small end for guiding the waves received from space at the large end to the translating means at the small end in order that the received waves may be absorbed by the translating means or for guiding to the large end for radiation out into space the waves excited by the translating means at the small end, and means extending through the tubes for connecting the translating means with means for evidencing the received waves absorbed by the translating means or with means for energizing the translating means to excite at the small end the waves to be radiated out into space.

27. An electric system having, in combination, an electromagnetic-wave-guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, an insulating sup: port fixed in the horn at the small end, and absorbing or exciting translating means supported by the support in the horn at the small end, the translating means comprising vacuum-tube apparatus and an antenna connected thereto, the antenna comprising substantially alined tubes, the vacuum-tube apparatus being disposed between the tubes, and means extending through the tubes for connecting the vacuum-tube apparatus with means for evidencing the received waves absorbed by the translating means or with means for energizing the means to excite at the small end the waves to be radiated out into space.

28. A radiator or absorber of radio waves comprising a horn interiorly provided with tubes constituting a radiator or absorber of radio waves, and translating apparatus carried in the horn by one of the tubes outwardly of any portion thereof that may be of substantially uniform section.

29. A radiator or absorber of radio waves comprising a horn having a larger end and a smaller end, the horn being interiorly provided with tubes constituting a radiator or absorber of radio from space at the large end to the translating 75 waves, a condenser, one of the tubes being directly connected to the horn, the other tube being connected to the horn through the condenser, translating apparatus carried in the horn by the said other tube,'and conductors connected to the translating apparatus extending through the said one tube, the said one tube constituting a shield for the conductors.

30. An electric system. for radiating electromagnetic waves into free space in a predetertermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, and translating apparatus for exciting the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space.

31. An electric system for receiving electromagnetic waves from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, and translating apparatus for receiving the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end.

32. An electric system for radiating electromagnetic waves into or receiving them from free space ina predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, and translating apparatus for exciting or receiving the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space or to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end.

33. An electric system for radiating electromagnetic waves into free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, and translating ap paratus for exciting the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the transverse dimension of the small end being comparable to the wave-length of the excited waves, and the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space.

34:. An electric system for receiving electromagnetic waves from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, and translating apparatus for receiving the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the transverse dimension of the small end being comparable to the wave-length of the received waves, and the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end.

35. An electric system for radiating electromagnetic waves into free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, the horn having a principal axis extending between the ends in the predetermined direction, means disposed in the horn at the small end outwardly of any'portion thereof that may be of substantially uniform cross section for exciting the electromagnetic waves comprising translating apparatus and an exciting rod disposed substantially at right angles to the principal axis, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space, and means for connecting the translating apparatus with sending apparatus.

36. An electric system for receiving electromagnetic waves from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, the horn having a principal axis extending between the ends in the predetermined direction, means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section for receiving the electromagnetic waves comprising translating apparatus and a receiving rod disposed substantially at right angles to the principal axis, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end, and means for connecting the translating apparatus with receiving apparatus.

37. An electric system for radiating electromagnetic waves into free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, a barrier, and translating apparatus disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier for exciting the electromagnetic waves, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space.

38. An electric system for receiving electromagnetic waves from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, a barrier, and translating apparatus disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier for receiving the eletromagnetic waves, the guiding surface extending substantial- 1y longitudinally of the predetermined direction and being shaped to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end.

39. An electric system for radiating electromagnetic waves into free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, a pipe joined to the small end, a conducting barrier disposed in the pipe near the junction of the pipe to the small end, and translating apparatus disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier for exciting the electromagnetic waves, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space.

40. An electric system for receiving electromagnetic waves from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, a pipe joined to the small end, a conducting barrier disposed in the pipe near the junction of the pipe to the small end, and translating apparatus disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier for receiving the electromagnetic waves, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end.

41. An electric system for radiating -electromagnetic waves into free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, and two elements one of which comprises a barrier and the other of which comprises translating apparatus disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier for exciting the electromagnetic waves, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space, and the relative positions of the elements being adjustable.

42. An electric system for receiving electromagnetic waves from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, and two elements one of which comprises a barrier and the other of which comprises translating apparatus disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier for receiving the electromagnetic waves, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end, and the relative positions of the elements being adjustable.

43. An electric system for radiating electroasoaoii magnetic waves into or receiving them from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, a pipe Joined to the small end, a conducting barrier adjustably disposed in the pipe near the junction of the pipe to the small end, and translating apparatus for exciting or receiving the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the pretetermined direction out into free space or to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end.

44. An electric system for radiating electromagnetic waves into or receiving them from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, the horn having a principal axis extending between the ends in the predetermined direction, and means adjustably disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section for exciting or receiving the electromagnetic waves, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space or to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end.

45. An electric system for radiating electromagnetic waves into or receiving them from free space in a predetermined direction comprising a wave-guide horn having a large end and a small end connected by a wave-guiding surface, a barrier, translating apparatus for exciting or receiving the electromagnetic waves disposed in the horn near the barrier at the small end, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the excited waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space or to guide the travel of the received waves in the horn and tangentially along the surface from the large end toward the small end, and conductors connecting the translating apparatus with apparatus outside the horn, the conductors extending through the barrier.

46. An electric system having, in combination, an electromagnetic-wave-guide horn substantially rectangular in cross section and having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, and absorbing or exciting translating means disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received ass-non from space at the large end to the translating means at the small end with a phase velocity substantially diflerent from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for radiation out into space the waves excited by the translating means at the small end.

47. An electric system having, in combination. a pipe one end of which is provided with an electromagnetic wave-guide horn substantially rectangular in cross section and having a small end joined to the said end of the pipe and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, an insulating support fixed in the horn at the small end near the pipe, and absorbing or exciting translating means supported by the support in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the horn having guiding walls between the large end and the small end for guiding the waves received from space at the large end to the translating means at the small end with a phase velocity substantially different from that of light in the medium of the horn in order that the received waves may be absorbed by the translating means or for guiding to the large end with a phase velocity substantially different from that of light in the medium of the horn for ratiation out into space the waves excited by the translating means at the small end.

48. An electric system for radiating electromagnetic waves into or receiving them from free space in a predetermined direction having, in combination, an electromagnetic wave guide horn substantially rectangular in cross-section and having a small end and a large end and connected by a wave-guiding surface, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, and absorbing or exciting antenna means for receiving or exciting the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the waves received from space at the large end in the horn and tangentially along the surface from the large end to the antenna means at the small end in order that the received waves may be absorbed by the antenna means or to guide the travel of the waves excited by the antenna means at the small end in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space.

49. A receiving system for receiving electromagnetic waves from free space in a predetermined direction having, in combination, an electromagnetic-wave-guide horn having a small end and a large end connected by a wave-guiding surface, the large end being electromagnetically open to space to permit the horn to receive modulated electromagnetic waves from space, absorbing translating means for receiving the electromagnetic waves disposed in the horn at the small end outwardly .of any portion thereof that may be of substantially uniform cross section, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the waves received from space at the large end in the horn and tangentially along the surface from the large end to the translating means at the small end in order that the received waves may be absorbed by the translating means, means for demodulating the received waves absorbed by the translating means, and means for connecting the translating means with the demodulating means.

50. A sending system for radiating electromagnetic waves into free space in a predetermined direction having, in combination, an electromagnetic-waveguide horn having a small end and a large end connected by a wave-guiding surface, the large end being electromagnetically open to space to permit the horn to radiate modulated electromagnetic waves out into space at the large end, exciting translating means for exciting the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section,

-means for energizing the translating means to excite at the small end the waves to be radiated out into space, means for connecting the translating means with the energizing means, and means for modulating the waves, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the modulated waves in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction for radiation out into free space.

51. An electric system for radiating electromagnetic waves into or receiving them from free space in a predetermined direction having, in combination, an electromagnetic wave guide horn having a small end and a large end and connected by a wave-guiding surface, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, and insulating support fixed in the horn at the small end, and absorbing or exciting translating means for receiving or exciting the electromagnetic waves supported by the support in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section, the translating means comprising vacuum-tube apparatus and an antenna connected thereto, and the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the waves received from space at the large end in the horn and tangentially along the surface from the large end to the translating means at the small and in order that the received waves may be absorbed by the translating means or to guide the travel of the waves excited by the translating means at the small end in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction out into free space.

52. An electric system for radiating electromagnetic waves into or receiving them from free space in a predetermined direction having, in combination, an electromagnetic wave guide horn having a small end and a large end, the large end being electromagnetically open to space to permit the horn to receive electromagnetic waves from space or to radiate electromagnetic waves out into space at the large end, the horn being provided with a conducting barrier at its small end, and absorbing or exciting translating means for receiving or exciting the electromagnetic waves disposed in the horn at the small end outwardly of any portion thereof that may be of substantially uniform cross section near the barrier, the guiding surface extending substantially longitudinally of the predetermined direction and being shaped to guide the travel of the waves received from space at the large end in the horn and tangentially along the surface from the large end to the translating means at the small end in order that the received waves may be-absorbed by the translating means or to guide the travel of the waves excited by the translating means at the small end in the horn and tangentially along the surface from the small end toward the large end and forward in the predetermined direction 19 out into free space. 

